A093420 Triangle read by rows: T(n,k) is the numerator of f(n, k) = (Product_{i = 0..k-1} (n-i))/(Sum_{i = 1..k} i) for 1 <= k <= n.

1, 2, 2, 3, 2, 1, 4, 4, 4, 12, 5, 20, 10, 12, 8, 6, 10, 20, 36, 48, 240, 7, 14, 35, 84, 168, 240, 180, 8, 56, 56, 168, 448, 960, 1440, 1120, 9, 24, 84, 1512, 1008, 2880, 6480, 10080, 8064, 10, 30, 120, 504, 2016, 7200, 21600, 50400, 80640, 725760, 11, 110, 165

Offset

1,2

Links

Table of n, a(n) for n=1..58.

Formula

T(n,n) = numerator(f(n, n)) = numerator(2*(n-1)!/(n+1)) = A090586(n).

Example

Triangle T(n,k) (with rows n >= 1 and columns k >= 1) begins as follows:
  1,
  2,  2,
  3,  2,  1,
  4,  4,  4, 12,
  5, 20, 10, 12,   8,
  6, 10, 20, 36,  48, 240,
  7, 14, 35, 84, 168, 240, 180;
  ...

Crossrefs

Cf. A090585, A090586, A093412, A093421 (denominators), A093422.

Sequence in context: A369028 A092565 A021452 * A104897 A185694 A305294

Adjacent sequences: A093417 A093418 A093419 * A093421 A093422 A093423

Keyword

nonn,easy,frac,tabl,less

Author

Amarnath Murthy, Mar 30 2004

Extensions

Edited and extended by David Wasserman, Aug 29 2006

Status

approved